Phosphoric acid has a variety of industrial, medical, and other uses. It may be produced with a “wet process,” using various acids to dissolve phosphate in source rock. The three types of acids typically used to accomplish the dissolution are: nitric, hydrochloric and sulfuric. Phosphates may be found in two rock types, igneous and sedimentary. Phosphate-bearing sedimentary rock is typically composed primarily of Francolite: Ca10(PO4)6-x(CO3)x(F,OH)2+x. The phosphate in the rock may require concentrating before it is of marketable quality. Reacting the phosphates in the rock with sulfuric acid may yield phosphoric acid and calcium sulfate (Gypsum) [Ca3(PO4)2+3H2SO4→2H3PO4+3CaSO4].
The gypsum may precipitate out of the solution as an insoluble salt that may be removed by filters to prevent the gypsum salt from coating the phosphate rock thereby inhibiting or halting the reactive process. Various types of filters may be used to remove the gypsum from the phosphate rock/acid solution; including belt filters, table filters, and tilting pan filters. Such filters may use a cloth filter to trap the gypsum particles as the liquid is pulled or drawn through the cloth by a vacuum process. The cloth filter may be removed and easily cleaned or replaced; however, it may be difficult to clean the filter supporting structure during operations. Such cleaning difficulty may result from gypsum crystal growth and solids plugging the openings through which the vacuum is applied. Cleaning may be beneficial since clogged openings in the filter support may reduce the efficiency of the filter during operation.
A current method of cleaning the filter support structure involves having at least one person manually direct a pressurized cleaning fluid, such as water, into contact with the filter structure. While this method may provide some level of cleaning, it also may consume a large amount of time and manpower; the operators of the associated cleaning apparatus may fail to clean portions of the filter structure; and the amount and time of contact of the water with the filter structure may be inconsistent, leading to non-uniform results.